1. Field of the Invention
The present invention relates to a liquid crystal display device and a fabricating method thereof, and more particularly to a thin film transistor substrate using a simplified fabrication process and a thin film patterning method applied thereto.
2. Discussion of the Related Art
A liquid crystal display device controls the light transmittance of a liquid crystal having a dielectric anisotropy using an electric field to display a picture. The liquid crystal display device includes a liquid crystal display panel displaying a picture using a liquid crystal cell matrix, and a drive circuit driving the liquid crystal display panel.
Referring to FIG. 1, a liquid crystal display panel of the related art includes a color filter substrate 10 and a thin film transistor substrate 20 that are bonded together with a liquid crystal 24 therebetween.
The color filter substrate 10 includes a black matrix 4, a color filter 6, and a common electrode 8 which are sequentially formed on an upper glass substrate 2. The black matrix 4 is formed in a matrix pattern on the upper glass substrate 2. The black matrix 4 divides an area of the upper glass substrate into a plurality of cell areas where the color filter is to be formed, and prevents light interference between adjacent cells and a reflection of external light. The color filter 6 is divided into red R, green G, and blue B areas in the individual cell areas to each transmit the red, green, and blue light. The common electrode 8 is formed of a transparent conductive layer formed over the entire surface of the color filter 6 to supply a common voltage Vcom that is fixed when driving the liquid crystal 24. In order to level the color filter 6, an overcoat layer (not shown) is formed between the color filter 6 and the common electrode 8.
The thin film transistor substrate 20 includes a thin film transistor 18 and a pixel electrode 22 which are in each cell area that are defined by crossing the gate line 14 and the data line 16 on a lower glass substrate 12. The thin film transistor 18 supplies a data signal from the data line 16 to the pixel electrode 22 in response to a gate signal from the gate line 12. The pixel electrode 22 formed of the transparent conductive layer supplies the data signal from the thin film transistor 18 to drive the liquid crystal 24.
The liquid crystal 24 having dielectric anisotropy rotates in accordance with an electric field generated by the data signal on the pixel electrode 22 and the common voltage Vcom on the common electrode 8 to control the light transmittance, thereby realizing a desired gray level.
The liquid crystal display panel further includes a spacer (not shown) to uniformly maintain a cell gap between the color filter substrate 10 and thin film transistor substrate 20. A ball spacer or a column spacer may be used as the spacer.
The color filter substrate 10 and the thin film transistor substrate 20 of the liquid crystal display panel are formed using a plurality of mask processes. One mask process includes a plurality of processes such as a thin film deposition (coating) process, a cleaning process, a photolithography process (hereinafter, referred to as “photo process”), an etching process, a photo-resist peeling process, and an inspection process.
Specifically, fabrication of the thin film transistor substrate includes a semiconductor process and requires a plurality of mask processes. Thus, its fabrication process is complicated, and it is a major portion of the manufacturing cost of the liquid crystal display panel. Accordingly, a thin film transistor substrate has been developed to reduce the number of mask processes from five mask processes that were typical.